Excerpt from a lecture given by Professor Pancake, a leading specialist in the geopolitics of surfing, in a South American airport concourse on December 18, 2012.<\/p>\n
To illustrate my point, I’m going to describe a surfer’s typical week: from the moment he wakes up to the moment he goes to bed, how the surfer, by analyzing the elements around him, will be able to put himself in a position to surf the best waves at the best time!<\/p>\n
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With the advent of the Internet and the proliferation of surf forecast websites, surfers have somewhat lost touch with meteorology, so let’s try to reacquaint ourselves with some basic knowledge.<\/p>\n
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First rule of thumb: water or air, what’s cold is heavy, creating the communicating vase effects of sea and air currents.<\/h2>\n
The Gulf Stream<\/strong> is generated by the North Equatorial Current and the Florida Current, which flows out of the Gulf of Mexico. Near the coasts of the Northern Hemisphere, seasonal temperature variations are significant, sometimes as much as 15\u00b0, and are due to solar radiation at the surface. However, in Portugal and Morocco, whose coasts are directly licked by the Gulf Stream, temperatures hardly vary at all, from 15\u00b0 to 22\u00b0, throughout the year. \n Coriolis force<\/strong>: in the northern hemisphere, any particle in motion is deflected clockwise (counter-clockwise in the southern hemisphere). In the Northern Hemisphere, anticyclonic updrafts turn to the right and depressions to the left. <\/p>\n \n \n Low pressure (depression: heavy air moving downwards) and high pressure (anticyclone: light air moving upwards)<\/strong> at the earth’s surface, shown on maps as narrower spirals for the depression and wider spirals for the anticyclone. In temperate latitudes, westerly winds predominate: cold air flows beneath warm air, creating a rotating system. The front line is where the two currents meet, as their different densities prevent them from mixing. <\/p>\n \n \n How to read an isobaric map: lines where pressure is the same, to visualize the shape and location of pressure fields.<\/p>\n Average pressure: 1015 Mb (millibars)<\/p>\n High pressure: 1035 Mb (anticyclone) potato shape with winds turning in the coriolis direction, in this case clockwise. Winds rather light. <\/p>\n Low-pressure areas: from 948 (ultra-high) to low (1010-1000), from medium (980-1000) to high (960-980 Mb). The wind is the air that moves from the anticyclones to the lows, “flowing” as if down a slope. The wind moves counter-clockwise. Rather circular onion shape. <\/p>\n The tighter the isobars, the higher the pressure and the stronger the winds, blowing almost parallel to the isobars<\/strong>.<\/p>\n \n When wind blows across a body of water, friction creates ripples on the surface, which spread out in the direction of the wind. Satellites or marine buoys (Gascogne Ouest Arcachon Buoy) measure wave height by averaging one-third of the highest waves. <\/p>\n \n You don’t need a very large body of water to generate waves: seas and lakes do.<\/p>\n Generated by the wind, it’s the Earth’s gravity that sustains the “surface gravity waves”… wrinkles and fine lines start out chaotically and end up gathering and consolidating, the shorter waves fading away to consolidate the longer ones.<\/p>\n When the waves leave the Windward Sea, they become swell, hardly visible on the surface, waves that will die on reaching a coastline. A journey that can last 12 days over 15,000 km in the Pacific. <\/p>\n \n Essential data :<\/p>\n Height (distance between crest and trough)<\/p>\n Wavelength (horizontal distance between two peaks)<\/p>\n The period is the time between two peaks \/ the celerity is the speed of the wave. <\/p>\n \n \n \n \n \n El Nino = abnormal warming of the surface of the western Pacific<\/strong> at Christmas time, resulting in changes in atmospheric pressure, causing drought, flooding, cyclones, landslides, coral bleaching… Warming exceeding 0.5\u00b0C… increases swell intensity in the North Pacific (January 1998)… Europe is little affected by the phenomenon. Global sea levels rise by 1 cm. <\/p>\n The phenomenon is then reversed: El Nina.<\/p>\n \n Tropical storms or cyclones<\/strong> are atmospheric disturbances in the tropical belt: called cyclones<\/strong> in the Indian Ocean and Australia, hurricanes<\/strong> in the Atlantic and typhoons<\/strong> in Asia, these disturbances are 600 to 2000 km wide and can last from 4 to 31 days.<\/p>\n \n \n \n There’s the traditional method of looking at isobar charts<\/strong>, consulting buoys<\/strong> and satellite data<\/strong>. Nowadays, websites<\/strong> interpret satellite and marine data for the surfer. For greater accuracy, the surfer can cross-reference all these data and get a fairly accurate view of conditions over the next 7 days. <\/p>\n \n Some surf weather forecast sites, there are many others:<\/p>\n \n Yadusurf<\/a><\/p>\n \n Windguru<\/a><\/p>\n \n Nautical charts on the net :<\/p>\n data.shom<\/a><\/p>\n \n \n To forecast actual wave heights, we need to take into account not only the swell’s orientation, but also its period. A swell with a period of more than 10 seconds, indicated at 1 metre, could be higher. On the other hand, a swell with a period of 5 seconds can be revised downwards, and will be short and sluggish. <\/p>\n When the period is long, the swell will be large and powerful, as is the case for most winter swells on the Landes coast. <\/p>\n \n Seasonal phenomena and geographical peculiarities must also be taken into account. <\/p>\n \n Generally, in stable periods, there is an alternation of onshore winds in the morning and offshore winds in the afternoon. At night, the land cools faster than the sea, and the air cooled on the ground is drawn towards the surface of the ocean, which has generated warm air that rises towards the sky (communicating vessel effect). <\/p>\n When the sun has warmed the ground, the phenomenon is often reversed around midday, with the warm land air rising and the sea air taking its place, falling back towards the coast. North-westerly on the Atlantic coast. <\/p>\n On the ocean side of France, the prevailing winds are oceanic north-westerlies.<\/p>\n \n Wind behaviour in a low-pressure scenario: a southerly wind heralds the arrival of a disturbance, veering westerly as it passes, then northwesterly as the low drags on. <\/p>\n \n Winter is characterized by a predominance of oceanic winds generated by the incessant passage of lows near the coast, while the other, more anticyclonic seasons benefit from morning off-shore breezes and a few entirely off-shore days. An open sky (thin cloud cover) often ensures continuity of the offshore breeze throughout the day, while a sudden clearing of the sky tends to warm the ground and trigger the arrival of thermal westerlies. <\/p>\n \n However, one of the universal rules of surfing is that wave quality is optimal in offshore winds!<\/strong><\/p>\n \n <\/p>\n The lows that cling to the mountains and wash over the Basque Country often spare the south of the Landes, and the thermals generally rise earlier over Vieux-Boucau.<\/p>\n \n The continental shelf stretches offshore to a depth of 200 meters, sloping just 0.2% to the slope that marks a clear break, and can extend for 65 km. This gradual slope cuts through the swell. In the Pacific islands, where the continental shelf is often non-existent, the swell hits the shore powerfully because it has not lost its speed. <\/p>\n \n \n \n A somewhat similar phenomenon occurs in Capbreton and Hossegor thanks to the presence of the Gouf, an underwater fault that originates just 300 meters from the coastline, opposite the harbor mouth. <\/p>\n \n
In the south of the Landes, by way of comparison, the water will drop to 12\u00b0 in January and peak at 24\u00b0 in August, barring extreme phenomena. As you head up the Gironde, the gap widens, with surface water temperatures as low as 9\u00b0 in winter. <\/p>\n1. Understanding an isobaric map :<\/h3>\n
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<\/a><\/p>\n<\/a> <\/p>\n2. The role of low pressure in wave formation<\/h3>\n
<\/a><\/p>\n3. Exceptional phenomena that upset seasonal trends and generate heavy swells<\/h3>\n
Predicting swell<\/h2>\n
1. Local wind: thermal<\/h3>\n
2. The Capbreton and Hossegor area benefits from a unique microclimate and topography.<\/h3>\n
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